<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>定宽居中</title>
    <link rel="stylesheet" type="text/css" href="../css/main.css">
    <style>
        #main {
            width: 800px;
            margin: 0 auto;
        }
    </style>
</head>

<body>
    <div id="main" class="main">
        <div class="head">Header</div>
        <div class="body">
            <div class="module-a">
                <div class="module-box">
                    <h2>模块 A</h2>
                    <ul>
                        <li>我是模块 A</li>
                    </ul>
                </div>
            </div>
            <div class="module-b">
                <div class="module-box">
                    <h2>模块 B</h2>
                    <ul>
                        <li>我是模块 B</li>
                        <li>我是模块 B</li>
                    </ul>
                </div>
            </div>
            <div class="module-c">
                <div class="module-box">
                    <h2>模块 C</h2>
                    <ul>
                        <li>我是模块 C</li>
                        <li>我是模块 C</li>
                        <li>我是模块 C</li>
                    </ul>
                </div>
            </div>
        </div>
        <div class="ft">Footer</div>
    </div>
</body>

</html>